It is well known, as illustrated in U.S. Pat. No. 3,799,204 to use a retrievable safety valve for insertion into a well conduit for controlling fluid flow through the conduit. In such installations, the well conduit includes a polished bore for receiving interference fit external seals on the safety valve for straddling the fluid control line from the well surface which provides control fluid to the safety valve for actuating a piston and cylinder assembly for opening and closing the safety valve. However, because the interference fit seals protrude from the exterior surface of the valve housing to provide a tight sealing relationship with the polished bore, the seals may be damaged as the safety valve is lowered through the well conduit. In addition, the safety valve housing generally includes a plurality of threaded sections which are joined together and sealed by elastomer type O-rings. These O-rings are subject to failure due to temperature limitations, corrosive well fluids and a limited life.
One feature of the present invention is the provision of seals on the exterior of the valve housing which are initially in a retracted protected position for limiting damage to the seals while the safety valve is run into the well conduit. The seals are then expanded either mechanically or hydraulically into an expanded and sealing engagement with the polished bore. Another feature of the present invention is the provision of a normally retracted but expandable seal adjacent to and above the safety valve closure member for sealing off well fluids between the interior and exterior of the valve housing and keeping the body from collapse. Another feature is the provision of a retrievable safety valve capable of withstanding both high and low temperature environments.